U.S. patent application Ser. No. 464,412, filed Feb. 7, 1983 by E. A. Flexman, now abandoned, and its copending continuation-in-part U.S. patent application Ser. No. 570,036, filed Jan. 16, 1984, discloses polyoxymethylene compositions having extraordinary impact resistance i.e. a Gardner impact value (measured according to ASTM D-3029, Method G, Geometry D using a 3.6 kg (8 pound) weight and injection molded 7.62.times.12.7.times.0.16 cm (3.times.5.times.1/16 inch) plaques of greater than 9 J (80 in-lb), which compositions consist essentially of
(a) 5-15 weight percent of at least one thermoplastic polyurethane, which polyurethane has a glass transition temperature of lower than 0.degree. C., and PA1 (b) 85-95 weight percent of at least one polyoxymethylene polymer, which polyoxymethylene polymer has a molecular weight of from 20,000 to 100,000, PA1 (a) greater than 15 weight percent and not more than 40 weight percent of at least one thermoplastic polyurethane, which polyurethane has a glass transition temperature of lower than -15.degree. C., and PA1 (b) at least 60 weight percent and less than 85 weight percent of at least one polyoxymethylene polymer, which polyoxymethylene polymer has a molecular weight of from 20,000 to 100,000, PA1 (a) 5-40 weight percent of at least one thermoplastic polyurethane, which polyurethane has a glass transition temperature of lower than 0.degree. C., and PA1 (b) 60-95 weight percent of at least one polyoxymethylene polymer, which polyoxymethylene polymer has a molecular weight of from 20,000 to 100,000. PA1 (a) 5-40 weight percent of at least one thermoplastic polyurethane, which polyurethane has a glass transition temperature of lower than 0.degree. C., PA1 (b) 0.2-1.0 weight percent of ethylene bis-stearamide, and PA1 (c) a complemental amount of at least one polyoxymethylene polymer, which polyoxymethylene polymer has a weight average molecular weight of from 20,000 to 100,000.
the above-stated percentages being based on the total amount of components (a) and (b) only, the thermoplastic polyurethane being dispersed throughout the polyoxymethylene polymer as discrete particles, and the composition having a Gardner impact value of greater than 9 J.
U.S. patent application Ser. No. 464,411, filed Feb. 7, 1983 by E. A. Flexman, now abandoned, and its copending continuation-in-part U.S. patent application Ser. No. 570,037, filed Jan. 16, 1984, discloses polyoxymethylene compositions having extraordinary toughness i.e. a notched Izod value (measured according to ASTM D-256, Method A) of greater than 375 J/m (7.0 ft-lb/in), which compositions consist essentially of
the above-stated percentages being based on the total amount of components (a) and (b) only, the thermoplastic polyurethane being dispersed throughout the polyoxymethylene polymer as a separate phase having an average cross-sectional size in the minimum dimension of not greater than 0.9 microns, and the composition having an Izod value of greater than 375 J/m.
The polyoxymethylene compositions disclosed in these two copending applications are compositions which can be improved by the present invention to give polyoxymethylene compositions characterized by improved mold release and reduced mold deposit characteristics.
U.S. Pat. No. 3,236,929, granted Feb. 22, 1966 to Jupa et al., discloses various compounds that are generally added to polyoxymethylene compositions to improve mold release characteristics of such compositions. Among the compounds disclosed as suitable for this purpose are long-chain aliphatic amides, e.g. ethylene bis-stearamide. However the polyoxymethylene compositions disclosed in this patent do not contain any thermoplastic polyurethane, and one can not extrapolate from polyoxymethylene compositions not containing any polyurethane to those containing 5-40 weight percent polyurethane with respect to additives for improving mold release and reducing mold sticking. This is evidenced by the fact that many of the mold release agents disclosed in the reference for use in polyoxymethylene compositions not containing any polyurethane are not suitable for use in polyoxymethylene compositions containing 5-40 weight percent polyurethane.